The present invention relates to electronic documents containing raster images and to pre-press graphic arts.
PostScript is a resolution-independent document format. PostScript fonts can be enlarged or reduced in size to accommodate any viewing resolution. When a viewer zooms in or out of a PostScript document, the text characters automatically scale accordingly. Thus it can be said that PostScript font characters are xe2x80x9cscalable.xe2x80x9d
Similarly, graphical objects based on vector graphics consisting of line segments and curves are also scalable. The line segments and curves can be enlarged or reduced in size by appropriately modifying the pixel coordinates of their control points.
Raster graphics, on the other hand, is not scalable. An image expressed in raster graphics is by its nature pixel resolution specific, and to enlarge or reduce the image involves digital image filtering and interpolation. Moreover, a raster image cannot be stretched beyond its original pixel resolution without introducing additional color data, such as interpolated color data, to the original color data.
In the field of pre-press graphic arts, routinely processed documents contain high resolution raster graphics, with quality levels at or near photographic quality. Such documents are typically stored electronically as very large files, the large size being due primarily to the raster images therewithin. As a result, such documents are unwieldy to process and to transmit. Traditionally pre-press service providers prepared sample proofs of jobs for their customers, and the customers came to the company shops in person to inspect the proofs, before the print productions were run. Today, however, many pre-press service providers use the Internet as a way to transfer jobs to customers for proofing. This has many advantages. The customer does not have to come to the shop in person. The customer does not have to inspect his job and mark his changes xe2x80x9con the spot.xe2x80x9d The customer can show his proof to others, and solicit their feedback. Proofs can be sent back and forth between the shop and the customer more often than before.
Use of the Internet for proofing has its shortcomings, though. On account of the large sizes of the files involved, when a customer proofs an electronic pre-press job on-line, there are unacceptable delays in interactively viewing the job, and in transmitting the job back and forth between the pre-press computer and a customer computer.
These delays can be mitigated somewhat by using only low resolution images in the document that is transmitted for proofing, but this is done at the expense of lost quality. A customer proofing a job with low resolution images is not able to inspect the quality of the imagesxe2x80x94which is one of the main objectives of proofing.
The present invention overcomes bandwidth limitations for on-line proofing of pre-print jobs by using a new type of document and a new type of client/server architecture. A standard document containing high resolution images is replaced by an image-less document, in which the high resolution images are removed and references to the images are substituted therefor. The high resolution images are stored on an image server, and transmitted using an Internet protocol that interactively transmits relatively small amounts of the image data, in response to a customer""s interactive viewing of a document. Specifically, the image server transmits image data used to generate a portion of an image at a specific resolution, necessary to display a portion of a page at a specific resolution requested by a customer. As the customer requests to see different portions of the page at different resolutions, the image server transmits additional image data as needed. The customer""s client computer caches image data it receives, so that whenever the same image data is needed a second time it is readily available in the client computer.
The present invention also provides an electronic document, including one or more raster images, which is scalable. The raster images are referenced within the document through links. The scalable document of the present invention can be enlarged or reduced to any desired resolution, making the entire document scalablexe2x80x94text characters, graphical objects and raster images.
Regardless of the viewing configuration, a raster image referenced within the scalable document of the present invention can automatically scale according to the viewing resolution. For example, suppose a 6xe2x80x3xc3x978xe2x80x3 photograph is converted to a high quality digital image by scanning at 600 dots per inch (dpi). This produces a 3,600xc3x974,800 pixel image, which is embedded into a page of the document.
When such a page is viewed at normal size on a view monitor having 72 dpi resolution, the referenced image is scaled to 432xc3x97576 pixels for purposes of display. If a user zooms in by a factor of two, to see a portion of the page containing the image at higher resolution, the referenced image is scaled to 864xc3x971,152 pixels. Thus the dimensions of the image referenced within the document automatically scale to twice their initial values. If the document is printed on a 300 dpi color printer, the referenced image is scaled to 1,800xc3x972,400 pixels in order to produce as high quality a print as possible using the color printer as an output device.
In a preferred embodiment of the present invention an original document is converted to an image-less document by removing the images contained within the original document and replacing them with references. The referenced images are stored on one or more image servers on the Internet or any other suitable computer network, and may be viewed using client computers. As the image-less document contains references to raster images, rather than the images themselves, the size of the image-less document of the present invention is relatively small.
Upon initial display, the document includes screen-size images. Upon delivery or print, the document will include images scaled to the appropriate device resolution.
Each client computer preferably downloads only that portion of the image data that is necessary for satisfying a user display request, as described hereinbelow. Continuing with the example above, the 3,600xc3x974,800 image in an uncompressed state occupies a total of 51.84 MB (at 3 bytes per pixel). High fidelity compression typically reduces this by an order of magnitude, to roughly 5 MB. Rather than requiring each client to download the entire 5 MB of image data, the present invention downloads that portion of the image data necessary to satisfy the user display request. The user display request is significantly less than the entire image size, since the maximum size image that can be viewed on a video monitor is the full video monitor pixel resolution, which may be 768xc3x971,024 for example. Similarly when saving or printing the document, the user may specify a resolution less than 600 dpi for the save operation, or the printer resolution may be less than 600 dpi, in which case the client only needs to download a portion of the full image data.
The present invention also provides a fragmenting tool for converting standard documents containing high quality images into image-less documents, and a composing tool for converting image-less documents into standard documents. The fragmenting tool is used for creating documents for interactive viewing over a client/server network. The composing tool is used for displaying document pages, or portions of document pages, on a video monitor, for saving documents containing high quality images at user specified resolutions, and for printing such documents at resolutions appropriate to specified output devices.
The present invention is useful in the graphic arts industry for providing efficient on-line proofing capability to customers for pre-press jobs that include high quality images, and overcomes transmission delays prevalent in prior art systems. It is also useful for console management of raster image processing (RIP) print jobs.
There is thus provided in accordance with a preferred embodiment of the present invention a method for on-line proofing of documents, including the steps of sending by a client computer a document request to a document server computer, transmitting a proof document from the document server computer to the client computer in response to the document request, sending by the client computer an image data request to an image server computer, transmitting image data from the image server computer to the client computer in response to the image data request, and combining the image data with the proof document.
There is further provided in accordance with a preferred embodiment of the present invention a system for on-line proofing of documents, including a first transmitter, situated within a client computer, sending a document request to a document server computer and sending an image data request to an image server computer, a second transmitter situated with the server computer transmitting a proof document from the document server computer to the client computer in response to the document request, and transmitting image data from the image server computer in response to the image data request, and a document composer combining the image data with the proof document.
There is still further provided in accordance with a preferred embodiment of the present invention a method for converting a document containing at least one image into a proof document, including extracting at least one image from the document, storing the at least one image as stored image data, and replacing the at least one image by at least one reference to the stored image data.
There is additionally provided in accordance with a preferred embodiment of the present invention a system for converting a document containing at least one image into a proof document, including a document fragmenter extracting at least one image from the document, a storage device for storing the at least one image as stored image data, and a reference inserter replacing the at least one image by at least one reference to the stored image data.
There is further provided in accordance with a preferred embodiment of the present invention a method for converting a proof document into a standard document using at least one reference to image data stored on an image server computer, the proof document containing layout information, including the steps of accessing the image data stored on the image server computer in accordance with the at least one reference, producing at least one image, and composing the at least one image with the proof document according to the layout information.
There is still further provided in accordance with a preferred embodiment of the present invention a system for converting a proof document into a standard document using at least one reference to image data stored on an image server computer, the scalable document containing layout information, including a data retriever accessing the image data stored on the image server computer, producing at least one image, and an image composer positioning the at least one image within the proof document according to the layout information.
There is additionally provided in accordance with a preferred embodiment of the present invention a method for viewing documents, including the steps of sending a document request to a document server computer, receiving a proof document from the document server computer in response to the document request, sending an image data request to an image server computer, receiving image data from the image server computer in response to the image data request, and combining the image data with the proof document.
There is yet further provided in accordance with a preferred embodiment of the present invention a system for viewing documents, including a transmitter sending a document request to a document server computer and sending an image data request to an image server computer, a receiver receiving a proof document from the document server computer in response to the document request, and receiving image data from the image server computer in response to the image data request, and a document composer combining the image data with the proof document.